Achieving the objectives of miniaturization and higher packing densities continue to drive the semiconductor manufacturing industry toward improving semiconductor processing in every aspect of the fabrication process. Several factors and variables are involved in the fabrication process. For example, at least one and typically more than one photolithography process may be employed during the fabrication of a semiconductor device. Each factor and variable implemented during fabrication must be considered and improved in order to achieve the higher packing densities and smaller, more precisely formed semiconductor structures.
In general, lithography refers to processes for pattern transfer between various media. It is a technique used for integrated circuit fabrication in which a silicon slice, the wafer, is coated uniformly with a radiation-sensitive film, the photoresist, and an exposing source (such as optical light, X-rays, or an electron beam) illuminates selected areas of the surface through an intervening master template, the photoresist mask, for a particular pattern. The lithographic coating is generally a radiation-sensitized coating suitable for receiving a projected image of the subject pattern. Once the image is projected, it is indelibly formed in the coating. The projected image may be either a negative or a positive of the subject pattern. Exposure of the coating through the photoresist mask causes a chemical transformation in the exposed areas of the coating thereby making the image area either more or less soluble (depending on the coating) in a particular solvent developer. The more soluble areas are removed in the developing process to leave the pattern image in the coating as less soluble polymer. The resulting pattern image in the coating, or layer, may be at least one portion of a semiconductor device that contributes to the overall structure and function of the device.
Due to the nature of photolithography, the integrity of each layer within a semiconductor structure must be maintained throughout the fabrication process in order to obtain a properly formed and fully operational device. However, at various stages of a typical fabrication process, defects may be introduced onto a layer and may become an indelible part of the completed device. Although some defects may be detected at or near the completion of fabrication, the repair of such defects consumes resources and reduces manufacturing efficiencies. In addition, some types of defects may not be detectable, let alone repairable, thus leading to increased production costs due to waste.
One example of a prominent type of defect is a defect formed while removing a photoresist layer from a semiconductor structure. The defects result from the interaction between the resist material and other materials employed to remove the photoresist layer. The resist and other materials form particles which may fill the spatial area on, above, and/or around some portion of the semiconductor structure. Therefore, some of the particles are undesirably deposited onto the structure and thus become defects on the structure.
Conventional end-point detection systems may find these defects, however, the detection of them occurs after the device is substantially fabricated. Thus, the conventional detection systems may be problematic for several reasons. In particular, the defects are perpetuated throughout the semiconductor structure, thereby inhibiting proper device performance and function. Hence, there is an unmet need for a system and/or method to mitigate such defects at an earlier stage in the fabrication process.